This invention relates to methods and arrangements for controlling the spacing between vehicles.
In methods for controlling the spacing of motor vehicles, the distance between a motor vehicle and a vehicle in front of it is controlled without any action by the driver by providing automatic control of the vehicle speed. For this purpose, a distance measuring arrangement emits directed electromagnetic waves such as laser or radar pulses which are reflected from the vehicle in front so that the spacing of the vehicle from a vehicle ahead and in the same lane is determined from the transit time of the pulses. The resulting vehicle spacing data are supplied to a control unit which controls the speed of the vehicle by accelerator or brake operation so that the distance from the motor vehicle in front matches a predetermined target spacing.
In conventional vehicle spacing control methods, the target distance is preassigned as a constant or corresponds to a defined safe distance which depends on the vehicle speed. With these arrangements it is not possible to vary the spacing from the vehicle in front depending, for example, on the traffic situation, or traffic density. For example, in heavy traffic, a shorter distance from the vehicle in front is often desirable in order to keep other vehicles from cutting in and thereby avoid the resulting braking of the vehicle but such spacing variation is not possible with conventional arrangements. Also, conventional arrangements cannot accommodate a driver's personal driving style, i.e. "sporting" drivers prefer a shorter distance from the vehicle in front and are skeptical of a distance control arrangement that fails to allow for this preference, whereas drivers with a "conservative" driving style choose to follow another vehicle with a greater margin of safety. In addition, there is a conventional spacing control method in which the driver can vary a preassigned target spacing by adjusting a potentiometer on the instrument panel. A disadvantage of this arrangement is that the driver must frequently manipulate an additional operating element, thus further burdening his task.
German Offenlegungsschrift No. 44 37 678 discloses a method in which the driver can establish a certain desired distance as the target distance as a function of speed by actuating the accelerator and/or the brake pedal. The selection of the desired spacing upon activation of the spacing control is accomplished when the driver, before activation of the spacing control, sets his individual desired distance, corresponding to the current speed of the vehicle, by using the accelerator or the brake pedal when following another vehicle. When the spacing from the vehicle in front corresponds to the spacing desired by the driver, the spacing control is activated by actuating a switch or operating lever, for example by actuating an operating lever on the steering wheel. The selection or variation of the desired spacing with the spacing control activated is accomplished by gradual actuation of the accelerator and/or the brake pedal to increase or decrease the spacing to another desired spacing. With the spacing control activated, the target spacing, depending on the preassigned desired spacing is determined as a function of the current vehicle speed. The target spacing as a function of vehicle speed and desired spacing may, for example, be plotted as a family of curves and stored in the control unit. Upon variation in the speed of the vehicle in front, and consequently the speed of the controlled vehicle, the target spacing is varied as a function of speed with the aid of the stored curves to maintain a corresponding following time. A disadvantage of this method is that, especially when setting the desired spacing upon activation, the vehicle operator commits himself for the ensuing period of time to that spacing reference or following time, which is then systematically followed according to the vehicle speed by way of the stored curves. But such spacing and following time values will not necessarily correspond to the individual's driving behavior so that the operator must continually correct the spacing using the brake or accelerator.
The publication "Abstandsregelung von Fahrzeugen mit Fuzzy-Control" (Spacing Regulation for Vehicles with Fuzzy Control), Tagungsband der 3. Dortnunder Fuzzy-Tager, Current Data-Processing Series, Springer 1993, discloses the determination of a spacing model depending on the type of driver and the weather conditions instead of using a fixed preassigned target spacing. The type of driver is ascertained by an external sensing system but there is no provision for dependable automatic recognition of the driver type.